The present invention relates to a means of connecting a pusher boat and a barge.
Barges have long been employed for the transportation of bulky cargoes in rivers, canals, lakes and harbours, and even in open sea. There are two conventional methods to move the barges, one being to tow by a tug boat and the other being to push by a pusher boat. The present invention relates to the latter case where the barge is connected with the pusher boat to form a pusher-barge combination system. More particularly, the invention relates to a means of connecting a pusher boat and a barge to form an improved pusher-barge combination system with excellent performance.
The method of connecting the pusher boat and the barge by means of ropes has widely been employed. In this method, however, the stern portion of the barge comes into contact with the bow portion of the pusher boat, and the relative vertical sliding of said two portions cannot be avoided. This relative sliding of these two watercraft causes heavy wear and tear of the buffer means provided between them. In addition, owing to relative pitching and yawing motions between these two watercraft, the connecting ropes are very often subjected to undue and excessive tension, which may often cause breaking of ropes, and the difficulties in navigation of pusher-barge combination systems in a heavy seaway have principally been due to these disadvantages. And, furthermore, the heavy connecting ropes must be handled by crew and, accordingly, connection and disconnection works require heavy and dangerous muscular labour.
These disadvantages inevitably involved in the conventional rope-connected pusher-barge combination system were eliminated by the introduction of a new means of connection (hereinafter to be referred to as the "former invention") invented by the present applicant and patented in the United States under the U.S. Pat. No. 3,935,831 (corresponding Canadian Pat. No. 1,026,164, French Pat. No. 75/11118, German Federal Republic Pat. No. 25 16 372, Spanish Pat. No. 436,590 and U.K. Pat. No. 1,465,207), in which the stern portion of the barge is provided with a notch or well for receiving the bow portion of the pusher boat with a suitable clearance left around said bow portion, and each side of said notch is provided with a vertical channel open toward the notch and formed of a bottom wall and two side walls, the latter of which being placed adjacent to the opening or entrance of the channel and provided with horizontal concavities extending from the entrance of said notch to said bottom wall and stepwise arranged from the top to the bottom on said side walls in such a manner that the two concavities placed at a same height on the opposite side walls may form a pair of concavities. On the other hand, both sides of the bow portion of the pusher boat are provided with hydraulically operable connecting pins, respectively, which can rotate relative to said pusher boat. The outer free end of each of said connecting pins has two convexities on its forward and rearward sides, so shaped as to automatically select and tightly engage with one of said pairs of concavities when said connecting pin is hydraulically extended outwards so that its outer free end is forcibly inserted into said channel. Thus, said two watercraft are firmly connected by the engagement of said connecting pins and said vertical channels.
Another embodiment of the former invention comprises a helmet mounted on the spherical head of each of said hydraulically operable connecting pins. This helmet has, on its forward and rearward sides, two convexities which will engage with one of said pairs of concavities when said connecting pin is extended outwards to connect said pusher boat to said barge. Said helmet mounted on said spherical head can turn to any direction within a limited small range so as to absorb bad influence of inevitable geometrical inaccuracies of welded structures of hulls on which the components of the connecting means concerned are mounted.
Between the pusher boat and the barge connected with each other by thus constructed connecting means of the former invention, there exists the relative pitching motion only and other relative motions such as rolling, yawing, heaving, drifting and surging are not permitted, and, as the result, the seaworthiness of the pusher-barge combination system can be remarkably improved as compared with the conventional rope-connected one.
The application in practice of the connecting means of the former invention has proved a remarkably high seaworthiness in high sea, while some disadvantages were disclosed particularly in the course of connection work. For inserting said connecting pins into said vertical channels, respectively, for the purpose of connection, the fore-and-aft positions of the axes of said connecting pins must be in coincidence with those of the centrelines of said vertical channels. Before being connected with each other, however, these two watercraft are floating freely and, in most cases, more or less oscillating freely independent of each other. Accordingly, it is practically impossible to keep said axes in coincidence with said centreline. Such a coincidence can be obtained and kept by means of an additional means of relative positioning according to Japanese Pat. No. 1,022,178 of the present applicant. Even with this means of relative positioning, it is not so easy to keep an accurate coincidence of positions for a certain long time necessary for connection, particularly when two watercraft are more or less oscillated by waves.
Another disadvantage is the abrupt turn of the connecting pin in the course of its extension for connection, when two watercraft are somewhat oscillated by waves. The outer free end of the connecting pin or the helmet mounted thereon is, when looked at from above, tapered toward its outer end, and the vertical channel of the barge has, when looked at from above, likewise has a trapezoidal shape, in its horizontal cross-section, wider at the entrance and narrower at the bottom for easily receiving the tapered end of said connecting pin or the tapered helmet. Two oblique side walls of the vertical trapezoidal channel, which correspond to the forward and rearward side walls of said channel in respect to the barge itself, are provided with concavities stepwise arranged from their upper ends to lower ends. The portion between two adjoining concavities forms a tooth-shaped convexity or swell. Accordingly, when the pusher boat is so small that it cannot stand still in inevitable small waves, or when the stern of the pusher boat is deviated to the port or starboard side by side or oblique waves so that the coincidence of the centrelines of two watercraft to be connected cannot be maintained, it may happen, though for a short time, that the outer free end of the connecting pin or the helmet mounted thereon may approach the forward or rearward side wall and, as the result, one of the two convexities on the forward and rearward sides of the pin or the helmet may enter one of the concavities on the corresponding side wall of the vertical channel and the other convexity may not enter any of the concavities on the opposite side wall. If the pusher boat is moved vertically by a wave at this moment, the convexity on the connecting pin or helmet which has already entered the corresponding concavity will be hit up or down by the swell adjacent to said concavity and, as the result, the connecting pin or the helmet will be turned. After this, the two convexities on the connecting pin or the helmet cannot enter their corresponding pair of concavities even when the connecting pin is further extended out and connection becomes impossible. Under such a circumstance, the connecting pins must once be retracted, the angular position of the turned connecting pin or the helmet rectified and connection tried again. When the oscillation of the pusher boat cannot be stopped because of incessantly coming waves, such a repeated trial may not assure any immediate connection in good order and an important delay of departure may occur. If the pusher boat must operate a number of barges alternately in a short service route, regular sailing schedule cannot be maintained because of frequent delay of departure. Similar accidental turn of the connecting pin or the helmet can take place even in the course of retraction for disconnection. The present invention is proposed in order to solve the above-mentioned problems involved in the connecting means of the former invention.